Thesis (MS )--Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: Robert L. Mokwa. Includes bibliographical references (leaves 100-109).

Thesis (Ph. D.)--School of Computing and Engineering and Dept. of Physics. University of Missouri--Kansas City, 2007. / "A dissertation in engineering and physics." Advisor: Anil Misra. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed July 30, 2008. Includes bibliographical references (leaf 93 ). Online version of the print edition.

<p> There is a great need for sensors that can infer the properties of polymer latices. Measuring ultrasonic wave travel parameters through a latex and calibrating these against polymer properties is one potential technique for measuring the polymer properties of a latex without separating the polymer particles from water. Ultrasonic longitudinal waves can be characterized by three travel parameters: the velocity, the attenuation and the frequency. For colloidal systems the attenuation will depend on molecular properties of the system inside a frequency window where diffraction and scattering are negligible.</p> <p> In this thesis the equipment for measuring ultrasonic waves is discussed and a measurement cell for measuring waves in liquids is designed and built. This equipment is used to measure the velocity and attenuation as functions of frequency for two sets of copolymer latices. These latices were measured separately using a combination of standard quality control analyses and polymer characterization techniques. It was discovered that the velocity of sound through latices does not differ significantly from the velocity for pure water while the ultrasonic attenuation of latices at solids concentrations of greater than 10 percent is much greater than the value for pure water.</p> <p> For the copolymer latices produced from styrene and methyl-methacrylate the attenuation measurements were all too similar to distinguish between changes in the properties of the latex. For the copolymer latices produced from styrene and butadiene, the attenuation and composition were related by an approximately linear relationship between 30 and 80 mole percent styrene. In this region, the attenuation spectra were regressed onto the property space using a linear multivariate algorithm called projection to latent structures. It was found that the attenuation is only useful for predicting latex properties that are related to composition in this range. Future work should focus on the use of a non-linear regression technique to model the behaviour of attenuation over the entire composition range and the use of independent analyses to better characterize some of the polymer properties such as crosslinking.</p> / Thesis / Master of Engineering (MEngr)

Essa dissertação aborda o tema de propagação de ondas de tensão em hastes metálicas retangulares. Este tipo de onda pode ser utilizada como base na verificação da integridade estrutural através de um ensaio não destrutivo (END). A propagação de ondas elásticas em sólidos apresenta muito potencial quando se deseja estimar a integridade de determinada estrutura. Porém para transformar esse fenômeno físico em uma técnica aplicável na detecção de danos, alguns passos devem ser seguidos, dentre eles: a compreensão das características de propagação da estrutura em estudo, in teração das ondas elásticas com defeitos, aten uação das ondas propagadoras devido a fontes de amortecimento e dispersão. Neste contexto o presente trabalho tem o principal foco no desenvolvimento de uma metodologia eficiente para a investigação da propagação de ondas de tensão em hastes retangulares metálicas, abordando o tema por diversos aspectos. No decorrer do mesmo são calcu ladas as curvas de dispersão de uma haste retangular com seção transversal de 15 x5 [rum], para uma faixa de frequência determinada [0,100 kHz], utilizando três metodologias distintas e realizando a comparação crítica entre elas. São realizadas investigações teóricas, de forma analítica e numérica (via análise explícita empregando elementos finitos) e uma inves tigação experimental das características de propagação da geometria referida. Também os efeitos da aten uação das ondas na geometria é estudado. Os resulta dos obtidos são discutidos procurando mostrar sua coerência e enfatizando a informação sobre o comportamento mecânico das ondas de tensão nesse tipo de estrutura, observando aspectos relevantes à concepção de técnicas de END que possi bilitem a avaliação da integridade dessas estruturas. / This dissertation addresses the issue of propagation of stress waves in metallic rectangular rods. This type of wave can be used as the integrity check structural integrity through a non-destructive test (NDT). The propagation of elastic waves in solids has a lot of potential when estimating the given structure integrity. But to turn this physical phenomenon in an applicable technique for the detection of damage, some steps should be taken, including: understanding of propagating characteristics of the structure under study, interaction of elastic waves with defects, attenuation of the propagating waves due to sources of damping and dispersion. In this context, the present work is the main focus in developing an effective methodology for investigating the propagation of stress waves in rectangular metal rods, addressing the issue by several aspects. During the same are calculated dispersion curves of a rod with rectangular cross section 15 x5 [mm], for a given frequency range [0,100 kHz], using three different methodologies and performing the critical comparison between them. Are performed theoretical investigations, in analytical and numerical form (via explicit analysis using finite element) and an experimental investigation of the propagation features said geometry. Also the effects of attenuation of the waves on geometry is studied. The results are discussed trying to show their consistency and emphasizing information about the mechanical behavior of stress waves in this type of structure, observing relevant aspects to the design of NDT techniques to enable the assessment of the integrity of these structures.

Orientador: Paulo José Amaral Serni / Banca: Claudionor Francisco do Nascimento / Banca: Fernando Pinhabel Marafão / Resumo: Este trabalho apresenta um estudo dos fenômenos de desequilíbrio e assimetria que podem ocorrer em sistemas trifásicos, no qual foram estudadas duas abordagens. A primeira delas é a abordagem tradicional de análise de fenômenos de desequilíbrio e assimetria, proposta por Fortescue, denominadas Componentes Simétricas ou Componentes de Sequência. Essa proposta desenvolvida no domínio da frequência foi estudada também no domínio do tempo, após sua adaptação. Isso porque as componentes simétricas generalizadas, nova abordagem de análise de desequilíbrio, está desenvolvida no domínio do tempo. Ambas as propostas de análise do desequilíbrio e assimetria trifásicos são aplicadas à sistemas trifásicos periódicos não senoidais. Enquanto que as componentes simétricas de Fortescue, para serem calculadas, necessitam que o sistema trifásico não senoidal seja decomposto nas harmônicas da série de Fourier, as componentes simétricas generalizadas podem ser aplicadas diretamente ao sistema não senoidal. O desenvolvimento de ambas as abordagens para um sistema periódico não senoidal resulta em relação entre ambas as propostas de análise de desequilíbrio e assimetria As relações entre as componentes simétricas generalizadas e as componentes simétricas de Fortescue são a principal contribuição deste trabalho. Baseado nas componentes simétricas generalizadas, novos indicadores de desequilíbrio são propostos. Os novos indicadores são comparados com os indicadores de desequilíbrio clássicos, os quais foram desenvolvidos a partir da proposta de Fortescue. Por fim, uma aplicação é desenvolvida na qual foram aplicados os conceitos estudados. Nesta aplicação, uma tensão trifásica não senoidal desequilibrada alimenta um motor de indução trifásico / Abstract: This work presents a study of the phenomena of unbalance and asymmetry which may occur in three-phase systems which two approaches were studied. The first one is the traditional approach of analysis of phenomena of unbalance and asymmetry, proposed by Fortescue, called Symmetrical Components or Sequence Components. This proposal developed in the frequency domain was also studied in the time domain after adaptation. This because of the generalized symmetrical components, new approach to the analysis of unbalance and asymmetry is developed in the time domain. Both proposals for analysis if the unbalance and asymmetry in three-phase systems are applied to the periodic non-sinusoidal three-phase systems. While the symmetrical components of Fortescue, to be calculated, require that the non-sinusoidal three-phase system is decomposed into harmonic Fourier series, the generalized symmetrical components can be applied directly to the non-sinusoidal system. The development of both approaches to a periodic non-sinusoidal system results in relationships between both proposals for analysis of unbalance and asymmetry. The relationships between the symmetrical components and the generalized symmetrical components of Fortescue are the main contribution of this work. Based on the generalized symmetrical components, new indicators of unbalance are proposed. The new new indicators are compared with the classical indicators of unbalance, which were developed from the proposed Fortescue. Finally, an application is developed with the concepts studied. In this application, an unbalanced non-sinusoidal three-phase voltage supplies a three-phase induction motor / Mestre

A comprehensive model for describing the fundamental mechanism dictating the interaction of ultrafast laser pulse with single crystalline silicon wafer is formulated. The need for establishing the feasibility of employing lasers of subpicosecond pulse width in Laser Induced Stress Waves Thermometry (LISWT) for single crystalline silicon processing motivated the work. The model formulation developed is of a hyperbolic type capable of characterizing non-thermal melting and thermo-elastoviscoplastic deformation as functions of laser input parameters and ambient temperature. A plastic constitutive law is followed to describe the complex elasto-viscoplastic responses in silicon undergoing Rapid Thermal Processing (RTP) annealing at elevated temperatures. A system of nine first-order hyperbolic equations applicable to describing 3-D elasto-viscoplastic wave motions in silicon is developed. The group velocities of certain selected frequency components are shown to be viable thermal indicators, thus establishing the feasibility of exploiting nanosecond laser induced propagating stress waves for the high-resolution thermal profiling of silicon wafers. Femtosecond laser induced transport dynamics in silicon is formulated based on the relaxation-time approximation of the Boltzmann equation. Temperature-dependent multi-phonons, free-carrier absorptions, and the recombination and impact ionization processes governing the laser model and carrier numbers are considered using a set of balance equations. The balance equation of lattice energy and equations of motion of both parabolic and hyperbolic types are derived to describe the complex thermo-elastoplastodynamic behaviors of the material in response to ultrafast laser pulsing. The solution strategy implemented includes a multi-time scale axisymmetric model of finite geometry and a staggered-grid finite difference scheme that allows both velocity and stress be simultaneously determined without having to solve for displacements. Transport phenomena initiated by femtosecond pulses including the spatial and temporal evolutions of electron and lattice temperatures, along with electron-hole carrier density, are found to be functions of laser fluence and pulse width. The femtosecond laser heating model that admits hyperbolic energy transport is shown to remedy the dilemma that thermal disturbances propagate with infinite speed. Non-thermal melting fluence is examined favorably against published experimental data. That it is feasible to explore femtosecond laser induced displacement and stress components for 1K resolution thermal profiling is one of the conclusions reached.

The task of a drill bit in percussive drilling is to transport the initial kinetic energy of the hammer to the workpiece in terms of stress waves. The efficiency of this transportation and the stresses that the drill bit is exposed to during the process is dependent on the nature of the stress waves. In hand-type hammer drilling, changing dimensions of the bit means changing conditions for the propagation and interaction of the stress waves. In this study, using finite element method, wave propagation and interaction in hand-type hammer drill bits is investigated with respect to drill bit dimensions. The main aim is to assess the effect of length and thickness on the efficiency and stress history of a hand-type drill bit. The results are evaluated in regard to workpiece hardness, which is a factor changing the effect of dimensions. In addition, chiseling test, which is used to prove bits under percussive loading, is carried out to detect differences between thin and thick drill bits, and the results are explained with the help of finite element simulations. Conclusions are drawn revealing the efficiency and stress history of drill bits under percussive loading with respect to thickness, length and workpiece hardness. Finally, it is seen that the real-life results of chiseling test are in agreement with the simulation results.

Techn. Univ., Habil.-Schr.--Braunschweig, 2006.

Not available / text

Essa dissertação aborda o tema de propagação de ondas de tensão em hastes metálicas retangulares. Este tipo de onda pode ser utilizada como base na verificação da integridade estrutural através de um ensaio não destrutivo (END). A propagação de ondas elásticas em sólidos apresenta muito potencial quando se deseja estimar a integridade de determinada estrutura. Porém para transformar esse fenômeno físico em uma técnica aplicável na detecção de danos, alguns passos devem ser seguidos, dentre eles: a compreensão das características de propagação da estrutura em estudo, in teração das ondas elásticas com defeitos, aten uação das ondas propagadoras devido a fontes de amortecimento e dispersão. Neste contexto o presente trabalho tem o principal foco no desenvolvimento de uma metodologia eficiente para a investigação da propagação de ondas de tensão em hastes retangulares metálicas, abordando o tema por diversos aspectos. No decorrer do mesmo são calcu ladas as curvas de dispersão de uma haste retangular com seção transversal de 15 x5 [rum], para uma faixa de frequência determinada [0,100 kHz], utilizando três metodologias distintas e realizando a comparação crítica entre elas. São realizadas investigações teóricas, de forma analítica e numérica (via análise explícita empregando elementos finitos) e uma inves tigação experimental das características de propagação da geometria referida. Também os efeitos da aten uação das ondas na geometria é estudado. Os resulta dos obtidos são discutidos procurando mostrar sua coerência e enfatizando a informação sobre o comportamento mecânico das ondas de tensão nesse tipo de estrutura, observando aspectos relevantes à concepção de técnicas de END que possi bilitem a avaliação da integridade dessas estruturas. / This dissertation addresses the issue of propagation of stress waves in metallic rectangular rods. This type of wave can be used as the integrity check structural integrity through a non-destructive test (NDT). The propagation of elastic waves in solids has a lot of potential when estimating the given structure integrity. But to turn this physical phenomenon in an applicable technique for the detection of damage, some steps should be taken, including: understanding of propagating characteristics of the structure under study, interaction of elastic waves with defects, attenuation of the propagating waves due to sources of damping and dispersion. In this context, the present work is the main focus in developing an effective methodology for investigating the propagation of stress waves in rectangular metal rods, addressing the issue by several aspects. During the same are calculated dispersion curves of a rod with rectangular cross section 15 x5 [mm], for a given frequency range [0,100 kHz], using three different methodologies and performing the critical comparison between them. Are performed theoretical investigations, in analytical and numerical form (via explicit analysis using finite element) and an experimental investigation of the propagation features said geometry. Also the effects of attenuation of the waves on geometry is studied. The results are discussed trying to show their consistency and emphasizing information about the mechanical behavior of stress waves in this type of structure, observing relevant aspects to the design of NDT techniques to enable the assessment of the integrity of these structures.